Well, they just build up over time and with extended cold. It’s not so much the coldness of the cold, but the extended time that it stays below freezing. At the elevation of that waterfall, it has probably had a hundred nights below freezing so far this winter, and the water is still flowing beneath and behind the ice, probably continually freezing a film of it.

Thanks! Well, the ice in the valley will be gone fairly soon, and I long to see the grass again. Up high though, over 7,000 feet there will be snow and frozen ground until next fall. Last year I remember taking a short snooze next to a pile of snow up above Vermilion Pass the first week of August.